1. Field
In general, a chiller (also referred to as a “turbo chiller”) supplies cold water to a cold water demand source, such as an air conditioning system, a computer server farm, factory equipment, laboratory equipment, etc., and the chiller is characterized by cooling the cold water by means of a heat exchange between cold waters circulating between a refrigeration system and the cold water demand source. The chiller is physically large and can be installed in large-scale buildings, such as an office building, factory, laboratory, or the like.
2. Background
The chiller may include a compressor, an evaporator, a condenser and an expansion valve. The compressor may include an impeller that rotates by a driving force of a driving motor, a shroud in which the impeller is received, and a variable diffuser that converts the kinetic energy of the fluid which is discharged by the rotation of the impeller into pressure energy.
The evaporator and the condenser may have a shell-in-tube structure. Cooling water and cold water (or other fluid) may flow inside the tube, and a refrigerant may be received inside the inner shell.
The cold water may be inputted to and discharged from the evaporator. The heat between the refrigerant and the cold water may be exchanged in the inner portion of the evaporator. The cold water is cooled in the course of passing through the evaporator. In addition, the cooling water may be inputted to and discharged from the condenser. The heat between the refrigerant and the cooling water is exchanged in the inner portion of the condenser. The cooling water is heated in the course of passing through the condenser.
Also, the liquid refrigerant condensed in the inside of the evaporator and the condenser may be maintained at a predetermined required level, and this level of liquid refrigerant may be adjusted through an expansion valve. The liquid refrigerant level may be changed during an initial start-up, during load fluctuations, or when setting temperature variation of the chiller. If the level of the liquid refrigerant in the condenser is not maintained at a constant level, the reliability of the turbo chiller may be decreased. Accordingly, the level of liquid refrigerant in the condenser may be measured, and the level of the liquid refrigerant may be adjusted.
Detecting and adjusting the level of the liquid refrigerant is discussed in Republic of Korea Laid-Open Patent Application No. 10-2014-0048620 (published date: Apr. 24, 2014). In the chiller (turbo chiller) disclosed in the preceding document, a controller directs a plurality of sensors to determine the level of the liquid refrigerant in the condenser, and further controls an expansion valve to adjust the level of the liquid refrigerant in the condenser based on the detected level of the liquid refrigerant. However, since the controller adjusts the expansion valve based on the detected level of the liquid refrigerant, a control stability problem may occur. In addition, the disclosed chiller may have a high manufacturing cost due to the multiple sensors and the complexity of the controller. The above reference is incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.